In a conventional blood purification therapy employed for treating renal failure and the like, hollow-membrane blood purification devices such as a hemodialyzer, a hemofilter and a hemodiafilter including, as a separation material, a hollow-fiber membrane using a polymer such as cellulose, cellulose acetate, polysulfone, polyethersulfone, polymethyl methacrylate or polyacrylonitrile have been widely used for purpose of removing uremic toxins and body wastes from blood.
As these hollow-fiber membrane blood purification devices, a polysulfone-based hollow-fiber membrane and a polyethersulfone-based hollow-fiber membrane are widely used because such membranes are excellent in reduction of the amount of blood to be extracorporeally circulated, high efficiency of removing uremic toxic substances from blood, and high productivity in module production, and are particularly capable of simultaneously attaining both high permeability and blood compatibility (Patent Documents 1 and 2).
In recent years, not only for purpose of removing uremic toxins and body wastes from blood but also for relieving oxidative stress apparently occurring in a patient on dialysis for a long period of time, attempts are made, for example, to use a separation membrane for eliminating a peroxide, that is, a causative substance of the oxidative stress, or to restore an antioxidant effect of a living body.
Patent Documents 3 and 4 propose a hollow-fiber membrane blood purification device in which a fat-soluble vitamin, such as vitamin E, having various physiological actions including an in vivo antioxidant effect, a biological membrane stabilizing action, and a platelet aggregation inhibiting action is introduced into a hollow-fiber membrane. It is known that a polysulfone-based hollow-fiber membrane and a polyethersulfone-based hollow-fiber membrane have high affinity with a fat-soluble vitamin capable of effectively inhibiting the oxidative stress caused through extracorporeal blood circulation, and hence the fat-soluble vitamin can be easily immobilized on the hollow-fiber membrane.
Meanwhile, cases of complications occurring in the blood purification therapy, such as disequilibrium syndrome presenting a symptom of headache, nausea or vomiting derived from an osmotic difference caused between blood in which a uremic toxin concentration has been abruptly lowered and a body tissue in which the uremic toxin concentration is easily retained, have been continuously reported even today, and these complications do not immediately induce risk of death or serious physical impediment but are painful to the patient.